In general, the shape of the ground contact portion (footprint) of a pneumatic tire is, for example, as shown at numeral 100 in FIG. 8, such that the length of the ground contact portion gradually reduces from the central portion toward the shoulder portion. However, with the rib pattern of the ground contact shape 100 uneven wear due to dragging in the vicinity of tread ground contact edge 102E is easily generated, and in order to suppress the above uneven wear the ground contact shape can be made close to a rectangular shape.
However, if the ground contact shape gets closer to rectangular, due to the variation in the conditions of tire manufacture and conditions of use, the length of the ground contact increases from the central portion to the shoulder portion to give the ground contact shape 104, and rib punch wear easily develops in the vicinity of the outer edge in the tire width direction at the second rib from the outer side rib 106 (the shaded portion of FIG. 9).
In order to solve this problem, a pneumatic tire has been proposed (see Patent Publication 1) with a ground contact pattern where the ground contact length first gets shorter from the central portion in the tire width direction to the tread ground contact edge side, and then the ground contact length gradually gets longer up to the tread ground contact edge.    Patent Publication 1: Japanese Patent Application Laid-Open (JP-A) No. 5-77608.